How can vaccinated foreign investors visit Greece to explore residency-by-investment options?

If you do not have a Greek social security number, you cannot get vaccinated in Greece. If you visit Greece, you would be required to stay in quarantine for 7 days.

Since Dec. 23, 2020, foreign investors can complete their applications from abroad, including applying for a Greek tax number, opening a Greek bank account, property acquisition/business plan submission/ implementation of financial products. All they have to do is sign a power of attorney at a Greek Consulate close to their current residence. You could follow the route of term deposit investment as a first step in order to acquire your permanent residency quickly. Later, when you visit, you could explore your alternatives.